In Depth Model Discussion, Analysis and Summaries

[BLAST FROM THE PAST]

Significantly, all major global models are programming a strong MJO wave to gain momentum in the western Pacific, and there's already a lot of cloudiness and thunderstorm activity there right now. This should help to increase the pressure on La Nina and send out a signal for anomalous mid latitude ridges as relative angular momentum edges upwards for the first half of the month and the GWO is nudged towards a phase 3-4 type evolution.

Basically a signal for the ridge to our east to remain in situ, joined with height rises over western Europe and the mean trough aligned to our west in the eastern Atlantic. That's a warm pattern, probably sustained for some time.

The significance of the tropical convection is that this MJO wave was in my book a weak affair with the next one in mid to late June the stronger. The fact that it is occuring relatively shortly after the last wave and of a similar forecast magnitude suggests that the atmosphere is trying to resurrect itself from the La Nina type base state that has been around since the late summer of 2010. This augers extremely well for a warm, settled spell of weather during June and into July.

Would seem a very good bet Stew, continuing your v good work it seems. Last 3rd May looks very warm indeed with thundery breakdown from west in early June and then a reset [i think June will be v similar in pattern to May....so a very good half term looking likely. Always maintaining dryer further S and E during breakdowns.

Enjoy summer folks...see you in Autumn.

BFTP

[Cecil Hogmanay Melchett]

Hi all,esp GP although this is an open winded poser.

I have family who have just returned from southern spain and apparently it has been extremely unsettled recently (as seen at the barcelona game the other night),now,i myself am jetting off at the end of this month and im getting a tad concerned about the lack of high pressure being projected in FI towards Iberia etc,does GP or any of the other more senior members have any thoughts on this?And more importantly their ideas as we head through may into June,again we have another GFS FI pointing to a very unsettled spell continuing in the med.

thanks for any replies as its the 1st time i will have been abroad in donkeys years and i really am getting concerned.

[mushymanrob]

Significantly, all major global models are programming a strong MJO wave to gain momentum in the western Pacific, and there's already a lot of cloudiness and thunderstorm activity there right now. This should help to increase the pressure on La Nina and send out a signal for anomalous mid latitude ridges as relative angular momentum edges upwards for the first half of the month and the GWO is nudged towards a phase 3-4 type evolution.

Basically a signal for the ridge to our east to remain in situ, joined with height rises over western Europe and the mean trough aligned to our west in the eastern Atlantic. That's a warm pattern, probably sustained for some time.

The significance of the tropical convection is that this MJO wave was in my book a weak affair with the next one in mid to late June the stronger. The fact that it is occuring relatively shortly after the last wave and of a similar forecast magnitude suggests that the atmosphere is trying to resurrect itself from the La Nina type base state that has been around since the late summer of 2010. This augers extremely well for a warm, settled spell of weather during June and into July.

unfortunately this does not now look like happening. both the ecm, and gfs, into fi lessens the high to our east but amlpifies the mid atlantic ridge, locking in the longwave to our north/northwest for some time IF the current FI outputs prove accurate.

[johnholmes]

unfortunately this does not now look like happening. both the ecm, and gfs, into fi lessens the high to our east but amlpifies the mid atlantic ridge, locking in the longwave to our north/northwest for some time IF the current FI outputs prove accurate.

I would not be too hasty in the long term, there are a number of possibilities I would suggest with the one from Stewart having about a 60-70% prob of being the right one in the time scale he mentions.

Always interesting with long or short term outputs to see what happens though.

[Glacier Point]

Indeed John, there is some interpretation to suggest here that: models are being too progressive in the removal of the mean ridge to our east; and, the re-set of the tough aligned to our west is coming onto the horizon of some of the longer range modelling, which tends to agree with where relative angular momentum is and will likely be in next 2-3 weeks. That said, I wouldn't rule out the temporary ridge to our west as it agrees with a phase 0 GWO and MJO altough we are likely to see some attempt to build the ridge back to the east in the next 10 day period.

Worth noting GFS 11-15 day ensemble mean builds the ridge back and ECM ensemble spread at t168 is moderate to large around the North Atlantic suggesting some degree of uncertainty about the modelling of the ridge.

Edited May 7, 2011 by Glacier Point

[Alex]

Hi GP some of the models ie the met office one shows the mid Atlantic linking up with our euro high in middle of next week however it may be more of a ridge?

Do you think I'n the shorter term the met offices 6-30 day outlook which says unsettled unsettled unsettled is probably far overdoing this up and coming more nasty spell?

[bluearmy]

Indeed John, there is some interpretation to suggest here that: models are being too progressive in the removal of the mean ridge to our east; and, the re-set of the tough aligned to our west is coming onto the horizon of some of the longer range modelling, which tends to agree with where relative angular momentum is and will likely be in next 2-3 weeks. That said, I wouldn't rule out the temporary ridge to our west as it agrees with a phase 0 GWO and MJO altough we are likely to see some attempt to build the ridge back to the east in the next 10 day period.

Worth noting GFS 11-15 day ensemble mean builds the ridge back and ECM ensemble spread at t168 is moderate to large around the North Atlantic suggesting some degree of uncertainty about the modelling of the ridge.

naefs remains solid in wanting to rebuild high anomolies close to our east once the shallow troughing has moved across and through to our east. the meto 30 dayer (new run issued yesterday) seems to concur with a pattern reflecting atlantic trough into iberia and sceuro block. mean southerly flow. i think the troughing coming across us will likely be a shortlived break in the overall mean pattern.

[geoffw]

so are we still looking at sustained warmth after this blip and when will the warmth roughly begin?

[johnholmes]

you do ask a lot of questions Geoff, nothing wrong to an extent but its impossible to give the detail you ask for at times. Can I ask that you carefully read the posts from GP especially and have a stab at seeing what you think things like temperature should do based on what has been posted.

I intend no offence but I do think you expect a little too much detail from such long range data outputs.

Have a read on the NW Guides about teleconnections and other places and try to build up your own understanding of these things-its not easy but its great to feel one is gaining a bit more understanding of them.

[geoffw]

read my post john i did not ask for detail, i asked for rough ideas.

read my posts more carefully john!!!

[Uncle_Barty]

Indeed John, there is some interpretation to suggest here that: models are being too progressive in the removal of the mean ridge to our east; and, the re-set of the tough aligned to our west is coming onto the horizon of some of the longer range modelling, which tends to agree with where relative angular momentum is and will likely be in next 2-3 weeks. That said, I wouldn't rule out the temporary ridge to our west as it agrees with a phase 0 GWO and MJO altough we are likely to see some attempt to build the ridge back to the east in the next 10 day period.

Worth noting GFS 11-15 day ensemble mean builds the ridge back and ECM ensemble spread at t168 is moderate to large around the North Atlantic suggesting some degree of uncertainty about the modelling of the ridge.

so are we still looking at sustained warmth after this blip and when will the warmth roughly begin?

To be fair to John, the info is all in there, Geoff, and that is as much detail as one could possibly give.

[mushymanrob]

I would not be too hasty in the long term, there are a number of possibilities I would suggest with the one from Stewart having about a 60-70% prob of being the right one in the time scale he mentions.

Always interesting with long or short term outputs to see what happens though.

fair comment john, i sincerely hope my pessimism proves to be unfounded! i mean no dis-respect to gp, im fully aware that his track record for long term trend spotting is often uncannily accurate, long before the model outputs start to show it

[BLAST FROM THE PAST]

For those looking for the warmth, it is coming and likely last 3rd May is the very warm/hot period some may seek. Looking at GPs thoughts I think that seems to be the same sort of timing. I see no long term flow from the northern quadrant. 00z ECM quite a change from the 12z, worth watching that.

BFTP

[Cecil Hogmanay Melchett]

For those looking for the warmth, it is coming and likely last 3rd May is the very warm/hot period some may seek. Looking at GPs thoughts I think that seems to be the same sort of timing. I see no long term flow from the northern quadrant. 00z ECM quite a change from the 12z, worth watching that.

BFTP

OZECM is absolutely awful.

ISee no evidence to back up this very warm period in may?

[Derp Patrol]

OZECM is absolutely awful.

ISee no evidence to back up this very warm period in may?

It's hardly awful for everywhere. For example here it looks like staying high teens or even low 20s for the next 4-5 days which is a bit above average for early May. Looking at FI in a model won't help you because it will just change each run, the pattern will start to show soon enough.

[bluearmy]

i think a lot of this belongs in the m/o thread chaps ???

[jethro]

Thought some of you may be interested in this new paper:

The Brewer-Dobson circulation and total ozone from seasonal to decadal time scales

http://www.atmos-chem-phys-discuss.net/11/13829/2011/acpd-11-13829-2011.pdf

[Alex]

Just a thought if gps thoughts are right on June will this mean the jet is pushed southwards I'n a similar vain to end of April across southern Europe and the Med?

[Iceberg]

Well we've finally ditched the La Nina.

http://www.bom.gov.au/climate/enso/

La Niña near its end

Issued on Wednesday 11 May | Product Code IDCKGEWWOO

"The 2010−11 La Niña event is nearing its end, with most indicators approaching neutral values. Climate models surveyed by the Bureau of Meteorology suggest that the Pacific Ocean will continue to warm over the coming months, with neutral conditions likely to persist through the austral winter.

Steady warming of the equatorial Pacific Ocean since mid-January has resulted in near-normal ocean temperatures. Atmospheric indicators of La Niña are now responding to these changes in the ocean and an active Madden Julian Oscillation, resulting in a weakening of trade winds, changes in cloudiness and an easing of typical La Niña pressure patterns. Likewise, the Southern Oscillation Index (SOI), which recorded its highest April value since 1904, has dropped from above +25 to +11 in the past fortnight.

The influence of the Indian Ocean Dipole (IOD) on Australian rainfall is currently neutral. A weakly positive IOD event has been forecast to develop during winter. In the past, positive IOD events have been associated with drier conditions over parts of Australia, particularly in the south east, during the winter and spring seasons. "

The big switch in the SOI also mentioned above, is the clearest illustrator yet we are possibly seeing the global switch from the current La Nina atmospheric set up to neutral one and all that entails.

This is one of the key factors IMO that will give us a warm spring and a warm summer unlike in more recent past years.

[feb1991blizzard]

The good news is that it is forecast to stay pretty close to neutral untill january.

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images3/nino12SSTMon.gif

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images3/nino3SSTMon.gif

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images3/nino4SSTMon.gif

http://www.cpc.ncep.noaa.gov/products/people/wwang/cfs_fcst/images3/nino34SSTMon.gif

[picog]

The good news is that it is forecast to stay pretty close to neutral untill january.

http://www.cpc.ncep....ino12SSTMon.gif

http://www.cpc.ncep....nino3SSTMon.gif

http://www.cpc.ncep....nino4SSTMon.gif

http://www.cpc.ncep....ino34SSTMon.gif

That's good if you like cold weather, right?

[feb1991blizzard]

That's good if you like cold weather, right?

I think so yes. Im pretty new to teleconnections but the La Nina of the past winter was responsible for the mild second half of winter according to most meteorologists / knowledgeable people on here although a weak La Nina wouldnt be too bad apparantely but this would depend on other teleconnections.

Edited May 13, 2011 by feb1991blizzard

[Paul]

Hi all, can we keep this thread for more technical and in depth discussion please. The general model discussion is a much more suitable place for a lot of the recent posts in here.

[Glacier Point]

A quickie..

Total angular momentum has now reached its highest value since February 2010 and probably the highest late spring / early summer since 2006 - such is the sustained run of low angular momentum that we've been in globally (note: all those really dodgy summers were characterised by strong negative tendency in angular momentum).

In the image below, which captures the growing influence of westerly wind bursts, look to the left hand side to see the latest westerly wind burst associated with the MJO.

This is about to weaken and easterly trades restrengthen a little.

This will take the GWO into phase 0 which signals the strengthening of the ridge in the mid-Atlantic allowing a weak tough to drop over the top into NW Europe.

http://www.esrl.noaa.gov/psd/map/images/gcm/gwo_40d.gif

However, don't panic. The weakening of the westerly wind bursts will reverse in June and a slight falling off in angular momentum is a pre-requisite to the trough in the Atlantic re-setting. Crucially, there's no indication of a resurgence of La Nina and we will start the next westerly wind burst from a much higher plateau than this time round. Confidence very much still high in the forecast Atlantic trough, ridge over western Europe scenarion.

[geoffw]

so your summer forecast still has a higgh chanceof verifying gp?